ARX788 in HER2-positive, Metastatic Breast Cancer Subjects (ACE-Breast-03)

Eligibility Criteria

• * Age ≥ 18 years and older
• * Life expectancy ≥ 6 months
• * Unresectable or metastatic breast cancer subjects
• * Presence of at least one measurable lesion per RECIST v 1.1
• * Subjects must have an adequate tumor sample available for confirmation of HER2 status
• * Subjects must have had prior treatment with no more than 5 prior regimens of systemic treatment in the metastatic setting. One of these prior treatments must have been treatment with T-DXd.
• * Subjects with stable brain metastases
• * Acute toxicities from any prior therapy, surgery, or radiotherapy must have resolved to Grade ≤1 as per the NCI-CTCAE v 5.0, except alopecia
• * Adequate organ functions
• * Willing and able to understand and sign an informed consent inform and to comply with all aspects of the protocol
• * History of allergic reactions to any component of ARX788.
• * Prior history of interstitial lung disease, pneumonitis, or other clinically significant lung disease
• * Any active ocular infections or chronic corneal disorders
• * History of congestive heart failure, unstable angina pectoris, unstable atrial fibrillation, or cardiac arrhythmia within 12 months prior to enrollment
• * Grade 3 to 4 peripheral neuropathy (NCI CTCAE v 5.0). Patients with Grade 2 neuropathy can be enrolled at investigator's discretion
• * History of unstable central nervous system (CNS) metastases
• * Current severe, uncontrolled systemic disease (eg, clinically significant cardiovascular, pulmonary, or metabolic diseases)
• * Any uncontrollable intercurrent illness, infection (including subjects with active, symptomatic Covid-19 infections), or other conditions that could limit study compliance or interfere with assessments
• * Exposure to any other investigational or commercial anticancer agents or therapies administered with the intention to treat malignancy within 14 days before the first dose of ARX788